How to attenuate noise in the rectifier circuit of a frequency converter?

To attenuate inverter rectifier circuit noise, both low-frequency harmonics and high-frequency switching noise need to be addressed separately. The rectifier bridge generates power frequency harmonic currents during operation, which are the main component of low-frequency conducted interference. High-frequency noise is primarily caused by diode reverse recovery and grid-side transients. Attenuation measures include: installing harmonic filters or power factor correction circuits at the AC input to reduce harmonic current injection into the grid at the source; setting up AC-side EMI filters, where the differential-mode inductor and large-capacity X capacitor attenuate low-frequency rectified noise; using electrolytic capacitors with sufficient capacity and low ESR on the DC bus side to smooth the DC voltage and reduce ripple; and connecting an RC snubber circuit in parallel across each rectifier diode to suppress high-frequency oscillations caused by diode reverse recovery. Optimizing the rectifier bridge installation reduces the loop area from the AC input line to the DC bus capacitor. For high-frequency conducted noise, the common-mode inductor in the filter, such as the CMZ7060A series, and the Y capacitor constitute the key attenuation path. Testing the conducted emission spectrum determines whether the exceedance is in the low-frequency or high-frequency range, allowing for targeted filtering enhancements. Eintech provides high-current EMI filters and safety capacitors for inverter inputs, which can effectively attenuate wideband noise generated by the rectifier circuit.